TW201526027A - Conductive composition and method for manufacturing the same, solar cell - Google Patents

Abstract

A subject of the invention is to provide a method for manufacturing a conductive composition in which good electric bonding can be realized when forming an electrode of a solar cell. The invention is a method for manufacturing a conductive composition for forming an electrode of a solar cell. The method includes: preparing silver powders, a tellurium-containing composition and a tellurium valence adjusting material; and adjusting a mixture of the silver powders, the tellurium-containing composition and the tellurium valence adjusting material in a manner that an average valence of tellurium containing in an interface of a substrate and the conductive composition when the conductive composition is coated on the substrate of the solar cell, and calcined is 4.3 to 5.1 so as to prepare the conductive composition.

Description

Method for producing conductive composition

The present invention relates to a method for producing a conductive composition for forming an electrode of a solar cell, a conductive composition obtained by the method, and a solar cell.

The present application claims priority to Japanese Patent Application No. 2013-240014, filed on Nov. 20, 2013, the entire disclosure of which is hereby incorporated by reference.

As a typical example of a solar cell that converts light energy of the sun into electric power, a solar cell using a crystalline germanium (single crystal or polycrystal) as a semiconductor substrate, a so-called crystalline germanium-based solar cell, is known. As the crystal lanthanide solar cell, for example, a single-sided light-receiving type solar cell (single cell) 110 shown in Fig. 2 is known.

The solar cell 110 has n-Si formed by pn junction on the light-receiving surface (upper surface in FIG. 2) side of a p-type germanium substrate (Si wafer: p-Si layer containing p-type crystalline germanium) 111. The layer 116 includes an anti-reflection film 114 containing titanium oxide, ceria or hafnium nitride, and a surface electrode (light-receiving surface electrode) 112 containing silver (Ag) on the n-Si layer 116. On the other hand, the back surface side external connection electrode 122 containing silver (Ag) similar to the light-receiving surface electrode 112 is provided on the back surface (the lower surface in FIG. 2) side of the p-type germanium substrate (p-Si layer) 111. The aluminum electrode 120 of the back surface field (BSF) effect and the p ⁺ layer (BSF layer) 124 formed by diffusion of aluminum to the p-Si layer 111. Here, as a related art related to the conductive composition for forming the light-receiving surface electrode 112, for example, Patent Document 1 to Patent Document 7 and the like can be cited.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2001-303400

[Patent Document 2] Japanese Patent Application Publication No. 2006-302890

[Patent Document 3] Japanese Patent Application Publication No. 2011-96747

[Patent Document 4] Japanese Patent No. 4754655

[Patent Document 5] International Publication No. 2012/020694

[Patent Document 6] International Publication No. 2012/141187

[Patent Document 7] International Publication No. 2012/144335

Further, typically, the light-receiving surface electrode of the lanthanide solar cell includes a linear bus bar electrode (connection electrode) and a plurality of thin-line grid electrodes (collecting electrodes) connected to the bus bar ). Since the light-receiving surface electrodes are formed on the light-receiving surface of the solar cell, a shadow loss occurs. Therefore, in order to The light-receiving area per unit area of the battery cell is enlarged, and the output efficiency per unit area of the battery cell, that is, the photoelectric conversion efficiency is improved, and it is required to realize thinning of the light-receiving surface electrode, especially the grid electrode having a large number of wires (fine-line) ). For example, it is required that the width of the grid electrode of about 130 μm in the conventional solar cell be 110 μm or less. However, for example, when the width of the grid electrode is made thinner, the ohmic contact between the light-receiving surface electrode and the n-layer is deteriorated, the contact resistance is increased, and the current density is lowered. Therefore, there is a problem that the conversion efficiency cannot be simply improved.

The present invention has been completed in the context of the above-described situation, and its purpose is A method of producing a conductive composition capable of achieving good electrical bonding when forming an electrode of a solar cell is provided. Moreover, another object of the present invention is to provide a conductive composition formed using the conductive composition and an electrode having the conductive composition to have excellent electrical characteristics (for example, an open circuit voltage, Filling factor or energy conversion efficiency) of the solar cell.

For example, as disclosed in Patent Document 3 to Patent Document 7, the conductive composition for forming an electrode of a solar cell is known to contain ruthenium in the form of a compound such as an oxide or as a glass constituent component. In the conductive composition, ohmic contact or the like can be improved. However, since the solar cell differs depending on its commercial form, for example, the composition of the substrate itself, or the required characteristics, etc., the actual situation is lack of detail for determining the constituent materials in the conductive composition. Guidance for the formula.

Under such circumstances, the inventors repeatedly studied with enthusiasm and found that The conductive composition having a ruthenium can change the valence of ruthenium in the formed electrode even when a conductive composition is produced using the same type of ruthenium source (for example, a ruthenium-containing glass composition or ruthenium oxide). (ie the electronic state of the Te atom). It is also known that regardless of the shape of the source, the valence of the ruthenium affects the characteristics of the solar cell, especially the ohmic contact between the substrate and the electrode, thereby completing the invention of the present application.

That is, according to the present invention, a method of producing a conductive composition for forming an electrode of a solar cell is provided. This manufacturing method is characterized by comprising the following steps (1) and (2).

(1) Preparation of silver powder, bismuth-containing composition, and valence price adjustment material.

(2) The average valence of cerium (Te) contained in the interface between the substrate and the conductive composition when the conductive composition is applied to the substrate of the solar cell and fired is 4.3 or more Further, in a mode of 5.1 or less, the composition of the silver powder, the ruthenium-containing composition, and the valence number adjusting material is adjusted to prepare a conductive composition.

According to the production method of the present invention, the composition of each constituent material constituting the conductive composition can be adjusted so that the ruthenium contained in the conductive composition exists in an optimum electronic state (electron arrangement) in the formed electrode. For example, in an electrode obtained by calcining a conductive composition under normal calcination conditions, ruthenium is oxidized to a state close to hexavalent (typically, a range of 5.2 to 5.5). However, in the present invention, by adjusting the formulation of each constituent material, the valence of ruthenium in the electrode calcined on the substrate to be used or the like is maintained in a state of being further reduced as described above. . Specifically, the formulation of the ruthenium-containing composition and the valence number adjustment material in the conductive composition is mainly prepared, and the electricity as the entire conductive composition is satisfied. Neutral conditions are imposed, and the average valence of cerium (Te) is achieved as a formulation of the stated range. Although the detailed mechanism is not clear, the electrical state of the electrode and the substrate can be preferably improved by the presence of germanium in the electronic state in the vicinity of the interface between the substrate and the electrode. Thereby, regardless of the form and amount of ruthenium in the conductive composition, the ruthenium atoms can be effectively present in the electrode to contribute to the electronic state of the low-resistance ohmic contact.

Furthermore, in the present specification, there is no particular limitation on the method of measuring the valence of hydrazine. system. For example, as a preferred measurement method for the valence of ruthenium, X-ray absorption fine structure (XAFS) analysis method or X-ray photoelectron spectroscopy (XPS) can be cited. ) and implemented.

Regarding XAFS, more specifically, the X-ray Absorption Near Edge Structure (XANES) analytical method can be used to excite non-occupied energy levels and quasi-continuous energy levels according to the inner shell electrons based on germanium atoms. The X-ray absorption spectrum of the energy at the time grasps the chemical state (electronic state) of the ruthenium atom. In the present specification, the valence of 碲 is as described later, and the average valence is based on the XAFS analysis device in the beam line BL14B2 using SPring-8 and by the transmission method. The measured XANES spectrum was calculated from the peak displacement amount around 4350 eV. Further, the absorption energy for calculating the average valence is not limited to the vicinity of 4,350 eV, and for example, the absorption energy such as the Te-K terminal or the L terminal may be used.

Further, regarding XPS, information on the elemental composition or chemical state of the surface can be obtained by observing the kinetic energy of the photoelectrons released by irradiating the surface of the sample under ultra-high vacuum with X-rays. Specifically, by analyzing the energy spectrum of the photoelectron, the ruthenium atom present on the surface of the substance can be identified, and the valence or combination can be obtained according to the chemical shift of the 碲 peak based on the narrow scan analysis. Status related information. The valence of 碲 can use the following result, which is obtained by using an XPS analyzer (manufactured by ULVAC-PHI Co., Ltd., PHI5000) using, for example, Al-Kα ray (hv=1486.6eV excitation) as a ray source. In the obtained XPS spectrum, for example, the peak value of Te-3d _5/2 in the vicinity of 576 eV is used as an index, and the average valence of 碲 is obtained from the relationship between the valence of ruthenium and the amount of binding energy displacement. Further, the peak value for calculating the average valence is not limited to Te-3d _5/2 , and may be other peaks such as Te-3d _3/2 (586 eV).

In a preferred embodiment of the method for producing a conductive composition disclosed herein, the cerium-containing composition is characterized in that it is a cerium compound powder containing cerium (Te) as a constituent element.

According to this configuration, it is preferable to adjust the blending method or the blending ratio of the crucible.

In a preferred embodiment of the method for producing a conductive composition disclosed herein, the ruthenium-containing composition is characterized in that it is a glass composition containing cerium (Te) as a constituent element.

According to this configuration, the ruthenium and the glass component can reach the substrate well together during the fire through, which can effectively contribute to the realization of the low-resistance ohmic contact. Further, by using a conductive composition containing a glass composition containing ruthenium, an electrode having a high bonding strength can be formed.

In a preferred embodiment of the method for producing a conductive composition disclosed herein, the glass composition is characterized in that it is a mixture of a basic glass component containing no antimony and a hafnium containing glass component containing antimony.

According to this configuration, the valence of the ruthenium after calcination can be more easily controlled, and the conductive composition having a high ohmic contact improving effect can be more easily produced.

In a preferred embodiment of the method for producing a conductive composition disclosed herein, the valence number adjusting material is characterized in that it comprises a material selected from the group consisting of Ti, V, Mn, Fe, Co, Ni, Cu, and a metal or metal compound of at least one metal element in the group consisting of Zn.

In the electrode after calcination, the metal element has a property that the electronic state is easily changed depending on the environment. With this configuration, the valence of ruthenium contained in the ruthenium-containing composition can be more preferably controlled. Further, by containing these metals or metal compounds, it is possible to improve the adhesion strength of the formed electrode and the reduction in contact resistance.

In another aspect, the present invention provides a conductive composition produced by any of the above-described production methods. Thereby, the prepared antimony component can be sufficiently contributed to the formation of a good (low-resistance) ohmic contact in the electrode after calcination. Further, the present invention also provides an electrode which can form an excellent adhesion. Conductive composition. Since the conductive composition adjusts the formulation in such a manner that it can exist in an optimum electronic state (electronic configuration) in accordance with the substrate to be used, an open circuit voltage can be realized in the case of forming an electrode of a solar cell. A solar cell having excellent filling characteristics and energy conversion efficiency and electric characteristics. According to this aspect, the present invention also provides electrical characteristics and reliability by providing an electrode formed using the conductive composition. Solar battery.

10‧‧‧Solar battery

11‧‧‧Substrate

12‧‧‧Photometric surface electrode (Ag electrode)

14‧‧‧Anti-reflective film

16‧‧‧n-Si layer (n ⁺ layer)

20‧‧‧Back electrode (aluminum electrode)

22‧‧‧Electrode for external connection on the back side

24‧‧‧p ⁺ layer (BSF layer)

110‧‧‧Solar battery

111‧‧‧p-type germanium substrate (p-Si layer)

112‧‧‧ Surface electrode (light receiving surface electrode)

114‧‧‧Anti-reflective film

116‧‧‧n-Si layer

120‧‧‧Aluminum electrode

122‧‧‧Electrode for external connection on the back side

124‧‧‧p ⁺ layer (BSF layer)

FIG. 1 is a cross-sectional view schematically showing an example of a configuration of a solar cell using the conductive composition of the present invention.

2 is a cross-sectional view schematically showing an example of a configuration of a solar cell using a conventional conductive composition.

Preferred embodiments of the present invention will be described below. In addition, in the present specification, matters other than those specifically mentioned and matters necessary for the implementation of the present invention (for example, a method of imparting a conductive composition on a substrate, a method of firing, a configuration of a solar cell, etc.) may be used. It is known to those skilled in the art based on design matters of the prior art in the field. The present invention can be implemented based on the contents disclosed in the present specification and the technical common sense in the field.

The method for producing a conductive composition disclosed herein is for the production of a conductive composition for forming an Ag electrode for use in forming a silver (Ag) electrode in a solar cell. As described above, the production method includes the steps of: (1) preparing a silver powder, a ruthenium-containing composition, and a ruthenium number adjustment material as a constituent material of the conductive composition; (2) coating the conductive composition The silver powder is adjusted so that the average valence of cerium (Te) contained in the interface between the substrate and the conductive composition when the substrate of the solar cell is baked is 4.3 or more and 5.1 or less Conductivity is prepared by formulating the cerium-containing composition and the valence number adjusting material Composition.

[silver powder]

The silver powder contained as a main solid component in the conductive composition disclosed herein is an aggregate of particles mainly composed of silver (Ag), and is typically an aggregate of particles containing a simple substance of Ag. However, if the aggregate of the particles of the Ag main body is a whole, the silver powder may be contained in a so-called "silver powder" as an alloy containing a small amount of impurities other than Ag or an Ag main body. Further, the silver powder may be produced by a conventionally known production method, and a special production method is not required.

The shape of the particles constituting the silver powder is not particularly limited. It is typically spherical, but is not limited to the so-called true spherical shape. In addition to the spherical shape, for example, a flake shape or an irregular shape may be mentioned. The silver powder may also contain particles of such various shapes. In the case where the silver powder contains particles having a small average particle diameter (typically several μm in size), it is preferred that 70% by mass or more of the particles (primary particles) have a spherical shape or a shape similar thereto. For example, it is preferable that 70% by mass or more of the particles constituting the silver powder is a silver powder having an aspect ratio (that is, a ratio of a long diameter of the particles to a short diameter) of 1 to 1.5.

Further, when an Ag electrode is formed on one surface (typically, a light receiving surface but also a back surface) of a substrate (for example, a Si substrate) constituting a solar cell, a desired size (line width, film thickness) can be achieved. The coating amount and coating form of the conductive composition are considered in the form of the shape and the like. Here, the silver powder which is preferable for forming the light-receiving surface electrode of the solar cell is not particularly limited, and it is preferable that the average particle diameter of the particles constituting the powder is 20 μm or less, preferably 0.01 μm or more. 10 μm or less, more preferably 0.3 μm or more and 5 μm or less, for example, 2 μm ± 1 μm. Here, the average particle diameter referred herein means a particle diameter at a cumulative volume of 50% in the particle size distribution measured by the laser diffraction/scattering method, that is, D50 (medium diameter).

For example, a silver (mixed) powder in which a plurality of silver powders (typically two kinds) having different average particle diameters are different from each other may be used, and the average particle diameter of the mixed powder is within the above range. By using the silver powder having the average particle diameter as described above, a dense Ag electrode which is preferably a light-receiving surface electrode can be formed.

The content of the silver powder in the conductive composition disclosed herein is not particularly limited, and when the conductive composition (solid content) is 100% by mass as a whole, it is preferably 50% by mass. The content ratio is adjusted so that the amount is 99% by mass or less, more preferably 65% by mass or more and 98% by mass or less, and for example, 75% by mass or more and 95% by mass or less is silver powder. When the content of the silver powder in the conductive composition to be produced is in the above range, an Ag electrode (film) having high conductivity and further improved denseness can be formed.

[碲 containing composition]

The ruthenium-containing composition can be used without any particular limitation as long as it is a powdery material containing cerium (Te) as a constituent element. Specifically, for example, it may be a simple substance of cerium (Te) or an organic compound containing cerium as a constituent element, a compound powder such as an inorganic compound, a powdery glass composition or the like. These may also be any two or more kinds of mixtures or composite compounds exemplified below.

[containing organic matter or antimony containing inorganic substances]

Examples of the organic compound include various decyl alcohols, tellurides, cerium oxides, tellurones and derivatives thereof. Examples of the ruthenium-containing inorganic compound include compounds of ruthenium and other metals, oxides, oxyacids, hydroxides, halides, sulfates, phosphates, nitrates, carbonates, acetates, and metal complexes. Bit compound). Typical examples of the inorganic or organic cerium-containing composition include tetragonal valence (Tetratellurafulvalene, TTeF); cerium oxide such as TeO ₂ , Te ₂ O ₃ , Te ₂ O ₅ , and TeO _{3 ;} ; tannic acid represented by Te(OH) ₆ ; potassium salt of meta-telluronic acid, sodium citrate, etc.; zinc telluride, aluminum telluride, cobalt telluride, antimony telluride, Deuterated tungsten, antimony telluride, antimony telluride, antimony telluride, antimony telluride, antimony telluride, antimony molybdenum and other deuterated metal compounds. Among the ruthenium-containing compositions, ruthenium may have values such as zero-valent, trivalent, tetravalent, pentavalent, and hexavalent. The ruthenium-containing composition used herein is preferably a compound in which ruthenium is present at a valence of 5 or 6 valent, and examples thereof include Te ₂ O ₅ , TeO ₃ , Te(OH) ₆ and the like.

[containing bismuth glass composition]

In addition, as the bismuth-containing glass component, various glass compositions containing ruthenium as a glass constituent component or a ruthenium compound-supporting glass composition in which a ruthenium compound is supported on the surface of a glass composition containing substantially no ruthenium may be considered. . That is, in the bismuth-containing glass component, the bismuth component is not a component which is deviated from the glass composition, but is a component constituting the glass composition itself, or is not free from the glass composition, but is present integrally. The bismuth-containing glass component can effectively act on a component which forms an Ag electrode as a light-receiving surface electrode of a solar cell from above the anti-reflection film by a burn-through method. Further, it may be an inorganic additive material that improves the adhesion strength to the substrate of the formed electrode.

By using a glass composition containing ruthenium as a constituent of glass, it can be lowered The softening temperature of the low glass composition can achieve a conductive composition having higher adhesion. The composition of the glass composition containing ruthenium as a glass component is not particularly limited, and for example, the composition shown below (the oxide conversion composition; the glass frit as a whole is 100 mol%) can be preferably used. Glass composition.

Hereinafter, the composition (oxide conversion composition) of the cerium-containing glass composition will be described in detail.

TeO ₂ functions as a component constituting a glass skeleton (network former) together with other elements, and has a function of lowering the softening point of the glass. In addition, the conductive composition for forming an electrode included in the solar cell can exhibit an effect of suppressing excessive erosion of the substrate during the burn-through. For example, the TeO ₂ may be contained in the glass composition in a proportion of about 70 mol% or less (further, 0 mol% in a glass composition containing no antimony described later). Since TeO ₂ is relatively expensive, it is costly when the amount of the compound is too large, and thus it is not preferable. It is preferable that the ratio of TeO ₂ is from 5 mol% to 65 mol%, more preferably from 10 mol% to 50 mol%.

SiO ₂ is a component constituting a glass skeleton (network former), and can be contained in the glass composition in a ratio of, for example, 0 mol% to 70 mol%. As the amount of SiO ₂ is increased, the solubility of the glass is lowered and the softening point is increased. When SiO ₂ exceeds, for example, 70 mol%, the burn-through characteristics are lowered, which is not preferable. In the case where the glass composition contains a glass network forming agent instead of SiO ₂ , the content of SiO ₂ may be 0 mol% (that is, substantially free of SiO ₂ ). In the case of containing SiO ₂ , the ratio of SiO ₂ is from 5 mol% to 65 mol%, more preferably from 10 mol% to 50 mol%, from the viewpoints of chemical stability, durability, workability, and the like of the glass structure. ideal.

B ₂ O ₃ exhibits a function of suppressing thermal expansion of the glass composition and lowering the viscosity and the melting temperature, and may be contained in the glass composition in a proportion of from 0 mol% to 40 mol%. When the amount of B ₂ O _{3 is} too large, crystals are easily precipitated during dissolution and cooling in the adjustment of the glass composition, which is not preferable. Since B ₂ O ₃ may be a factor causing a decrease in long-term durability (especially long-term high-temperature durability), the content of B ₂ O ₃ may also be 0 mol% (that is, substantially free of B ₂ O ₃ ). It is preferably a ratio of B ₂ O _{3 of} from 1 mol% to 30 mol%, more preferably from 5 mol% to 25 mol%.

Bi ₂ O ₃ is an optional component and is a component that adjusts the coefficient of thermal expansion. Moreover, physical stability can also be improved by including a multi-component system for the glass bonding material. The ratio of Bi ₂ O ₃ in the glass composition is, for example, preferably in a proportion of about 1 mol% to 30 mol%, more preferably about 5 mol% to 25 mol%.

PbO is an optional component to reduce the softening point of the glass, and may be contained, for example, in a ratio of from 0 mol% to 65 mol%. The PbO content may be 0 mol% (i.e., substantially free of B ₂ O ₃ ) in consideration of human health and environmental impact. In the formulation containing PbO, the proportion of PbO is, for example, preferably from 10 mol% to 50 mol%, more preferably from 30 mol% to 40 mol%.

About alkaline earth metal components (MO: specifically, MgO, CaO, ZnO, At least one of SrO and BaO is not necessarily an essential component, but is a component of a network modified oxide (network modifier) which is useful for controlling the thermal stability of the glass composition. In the case of containing the above, for example, the ratio may be from 1 mol% to 25 mol% in total, or more preferably in total. It is a ratio of about 1 mol% to 10 mol%.

The alkali metal component (RO: specifically, at least one of Li ₂ O, Na ₂ O, and K ₂ O) is not necessarily an essential component, but may be contained as a component that increases the meltability of the glass composition. Any one or more. These components may be contained, for example, in a proportion of about 1 mol% to 15 mol%, more preferably, for example, 1 mol% to 7 mol%.

The glass composition contained in the conductive composition disclosed herein may be composed only of the typical glass constituent components as described above, or may be contained as long as the effects of the present invention are not significantly impaired. Any component other than that. Examples of such an additive component include, in the form of an oxide, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , WO ₃ , V ₂ O ₅ , Nb ₂ O ₅ , FeO, CuO, SnO ₂ , and P ₂ O. ₅ , La ₂ O ₃ , CeO _2, etc. Further, an additive (a known clarifying agent, a coloring agent, or the like) which is conventionally used for such a glass bonding material may be contained as needed. The proportion of these additional constituent components or various additives is preferably less than about 5 mol% (typically less than 4 mol%, for example less than 1 mol%) of the entire glass composition. In addition to this, it is of course allowed to mix components other than those shown in the above composition, and it is an unavoidable impurity derived from a raw material or a manufacturing process.

On the other hand, it is not necessarily limited to this. In a preferred embodiment, a formulation containing substantially no arsenic (As) component other than the lead (Pb) component may be used. Since the arsenic component or the lead component adversely affects the human body or the environment, it is not preferable from the viewpoint of environmental performance, workability, and safety.

As the bismuth-containing glass composition as described above, more specifically, for example The following glass L, glass M, and glass N are mentioned as a preferable example.

[Glass L]

SiO ₂ : 9 mol% or more and 53 mol% or less

B ₂ O ₃ : 1 mol% or more and 7 mol% or less

PbO: 10 mol% or more and 57 mol% or less

TeO ₂ : 10 mol% or more and 70 mol% or less

[Glass M]

SiO ₂ : 9 mol% or more and 65 mol% or less

B ₂ O ₃ : 1 mol% or more and 18 mol% or less

PbO: 9 mol% or more and 65 mol% or less

Li ₂ O: 0.6 mol% or more and 18 mol% or less

TeO ₂ : 10 mol% or more and 70 mol% or less

[Glass N]

Bi ₂ O ₃ : 10 mol% or more and 29 mol% or less

B ₂ O ₃ : 10 mol% or more and 33 mol% or less

SiO ₂ : 0 mol% or more and 20 mol% or less

ZnO: 10 mol% or more and 30 mol% or less

TeO ₂ : 10 mol% or more and 60 mol% or less

Total of Li ₂ O, Na ₂ O, and K ₂ O: 8 mol% or more and 21 mol% or less

When any of the glass L, the glass M, and the glass N described above is used for the conductive composition of the present invention, the electrical characteristics of the solar cell can be particularly improved. That is, as a glass composition which exhibits a burn-through effect, for example, glass L and glass which are lead-containing glass are used. The formation of the light-receiving surface electrode of the solar cell can be preferably performed by either M or the glass N as the lead-free glass.

On the other hand, in the ruthenium compound-supporting glass composition, the ruthenium compound is The glass composition as a carrier is inseparably integrated with each other, and is mainly contained as a crystal phase rather than as a component constituting the glass. For example, specifically, it is a state in which one or a plurality of cerium compound particles are bonded to each other and supported on a glass medium with respect to one scaly or powdery glass medium. The glass medium carrying the ruthenium compound particles may be further combined with a plurality of or the like. Here, the relative size of the glass medium and the cerium compound particles is not particularly limited, and either of them may be large or may be the same size. Just keep the relative positional relationship between the two.

If attention is paid to the structure of the ruthenium compound supporting the glass composition, The material-supporting glass composition has a structure in which a glass composition (glass phase) and a crystalline cerium compound phase (crystalline phase) are interfacially interfacial and integrated. Here, the glass phase has a glass containing substantially no cerium (Te) as a main component. That is, the glass phase may contain Te, but it is not contained as a main component for forming a glass skeleton, but may be contained as a secondary component. Further, the ruthenium compound phase is a crystal having a ruthenium compound as a main component (for example, a ruthenium compound is intended to be 50% by mass or more), and has a crystal structure, and in this respect, it can be clearly distinguished from the glass phase. The glass phase can comprise a glass phase, and a plurality of glass phases can also be present. Further, the ruthenium compound phase may contain one ruthenium compound phase, and a plurality of ruthenium compound phases may also exist. For example, in a glass phase, a plurality of ruthenium compounds having different compositions may be integrated, and a plurality of glass phases having different compositions may be integrated with a plurality of ruthenium compounds having different compositions.

Since the glass phase and the ruthenium compound phase also have a component in which the components at the joint interface are diffused, for example, the components may be contained in the vicinity of the interface. That is, it may be a form in which the components in the vicinity of the interface are not uniform. Typically, for example, the glass phase may contain Te in the vicinity of the interface with the ruthenium compound phase. However, it may be in the form of no Te near the center of the glass phase. Further, depending on the size of the glass phase, a form in which Te is contained in the vicinity of the center may be considered. However, in this case, it is also understood that Te does not exist as a main glass network forming agent (ie, a glass skeleton). Further, the ruthenium compound phase may contain a constituent component of the glass phase in the vicinity of the interface with the glass phase. In this case, the constituent component of the glass phase is partially contained as a constituent component of the cerium compound.

That is, in the ruthenium-supporting glass medium, the glass phase and the ruthenium compound are joined at the interface, and although the components in the vicinity of the interface are diffusible, there is no case where one phase is completely incorporated into the other phase, essentially It exists as a separate and distinct phase.

The shape of the glass composition carrying the ruthenium compound (which may be a glass phase, the same applies hereinafter) in the ruthenium-supporting glass composition is not particularly limited, and may be, for example, a scaly shape obtained by pulverizing glass or the like. Powdered glass. Further, the composition is not particularly limited, and may be the same as a glass medium or the like used for such a conductive composition from the prior art.

Examples of such a glass medium include lead-based glass, zinc-based glass, borosilicate glass, and alkali-based glass; and glass containing cerium oxide or cerium oxide; or a combination of two or more thereof. Glass. The composition of the glass medium can be considered in accordance with the composition of the bismuth-containing glass composition (other than TeO ₂ ). More specifically, for example, a glass composition having a representative composition (the oxide-converted composition; the entire glass medium is 100 mol%) as shown below is preferable.

[Glass L']

SiO ₂ : 9 mol% or more and 53 mol% or less

B ₂ O ₃ : 1 mol% or more and 7 mol% or less

PbO: 46 mol% or more and 57 mol% or less

[Glass M']

SiO ₂ : 20 mol% or more and 65 mol% or less

B ₂ O ₃ : 1 mol% or more and 18 mol% or less

PbO: 20 mol% or more and 65 mol% or less

Li ₂ O: 0.6 mol% or more and 18 mol% or less

[Glass N']

Bi ₂ O ₃ : 10 mol% or more and 29 mol% or less

B ₂ O ₃ : 20 mol% or more and 33 mol% or less

SiO ₂ : 0 mol% or more and 20 mol% or less

ZnO: 15 mol% or more and 30 mol% or less

Total of Li ₂ O, Na ₂ O, and K ₂ O: 8 mol% or more and 21 mol% or less

In addition, the representative composition is representative, and good adhesion to a substrate, formation of an electrode film, corrosion resistance against a reaction reflection film, good ohmic contact, and the like are obtained. Various components may be adjusted, or a glass modifying component (an alkali metal element, an alkaline earth metal element, or various other glass forming components) may be further added.

Further, the ruthenium compound supported on the glass composition is not particularly limited, and for example, various ruthenium compounds exemplified above can be considered. The ratio of the ruthenium compound supported on the glass medium is not particularly limited. For example, the ruthenium compound is preferably used in terms of mass per 100 parts by mass of the glass medium in terms of cerium oxide (TeO ₂ ). The ratio of 20 parts by mass to 60 parts by mass is more preferably 30 parts by mass to 50 parts by mass.

The conductive composition is considered by the above-mentioned ruthenium-supporting glass composition In the case where the ruthenium compound and the glass composition are present in a preferred state, there is no excessive uniformity or excessive unevenness, and there is no excessively close or excessively distant. From the time of preparation of the conductive composition, the application and drying of the conductive composition need not be continued until the glass component is melted by firing, and the preferable positional relationship is maintained. By the conductive composition containing such a ruthenium-supporting glass composition, an electrode having low resistance and high energy conversion efficiency can be formed as compared with a silver paste containing a ruthenium compound as a single paste constituent component. In addition, the conductive composition containing the ruthenium-supporting glass composition can form an electrode having a higher bonding strength than a conductive composition containing a glass medium containing ruthenium as a network-forming agent. That is, an electrode having high adhesion strength (for example, welding strength) and low contact resistance can be formed.

[Basic glass composition]

Further, the bismuth-containing glass disclosed herein does not necessarily need to be all of the glass compositions and/or ruthenium-supporting glass compositions containing ruthenium as a glass constituent component as described above. For example, various glass compositions and/or ruthenium-supporting glass compositions containing ruthenium as a glass constituent component and basic bismuth-free glass components (non-ruthenium-containing glass) used for such a conductive composition from the prior art may be used. )Mixed use. The composition of the basic glass component is not particularly limited, and for example, it can be considered in accordance with the composition of the above-described bismuth-containing glass composition (other than TeO ₂ ). More specifically, a glass having any one of the above-described glass L', glass M', and glass N' is exemplified as a preferred example. The ratio of the bismuth-containing glass to the basic glass component in this case can be appropriately determined by referring to the total amount of the glass component of the conductive composition and the amount of ruthenium contained in the bismuth-containing glass.

The preferred ratio of the glass component to the conductive composition (solid content) is not limited thereto, but is preferably 0.5% by mass or more and 5% by mass or less, preferably 0.5% by mass or more and 3% by mass or less. More preferably, it is 1% by mass or more and 3% by mass or less.

Also, since the content of the cerium-containing composition also depends on the cerium-containing composition used. Although the form of the object cannot be generalized, the average valence of cerium (Te) contained in the interface between the substrate and the conductive composition when the conductive composition is applied to the substrate of the solar cell and calcined is 4.3 or more. And 5.1 or less, and it is determined by adjusting the ratio of the silver powder and the valence number adjustment material. For example, when the cerium-containing composition described in the examples described later is used as the cerium-containing composition, the cerium-containing composition is used when the total amount of the conductive composition (solid content) is 100% by mass. The ratio is preferably 0.5% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 35% by mass or less, and for example, 5% by mass or more and 25% by mass or less.

[碲价量调整]

As the valence number adjusting material, a powder containing a compound containing an element which is relatively easily changed in oxidation number can be preferably used. For example, consider a price of +3 A transition metal of an ion, a typical metal, and a metal containing a rare earth element or a compound thereof. More preferably, it is a metal or a compound thereof which is an element belonging to Groups 3A to 3B of the periodic table, and a transition metal element belonging to Group 3A to Group 2B of the periodic table is typically considered, and particularly preferably It is conceivable to contain ruthenium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel as the first transition element (3d transition element). A powder of a metal of (Ni), copper (Cu), and zinc (Zn) or a compound thereof. More preferably, it is a powder containing a metal of Fe, Co, Ni, Ti or an oxide thereof, and further may be limited to Ni or NiO. These powders may be contained alone or in combination of two or more.

The average particle diameter of the particles constituting the powders is preferably 1 nm or more and 200 nm or less, preferably 5 nm or more and 200 nm or less, more preferably 15 nm or more and 200 nm or less.

The amount of valence adjustment material can be applied to the conductive composition too The average valence of cerium (Te) contained in the interface between the substrate and the conductive composition when the substrate of the positive electrode is baked is 4.3 or more and 5.1 or less, and is blended with the silver powder and the cerium-containing composition. The ratio is determined. By adjusting the amount of the valence to adjust the content of the material, the average number of enthalpies can be effectively controlled. The content of the valence number adjustment material is not critical, and when the total amount of the conductive composition (solid content) is 100% by mass, the ratio of the valence number adjustment material is approximately 0.5% by mass or less. The degree is the benchmark. It is preferably 0.001% by mass or more and 0.3% by mass or less, more preferably 0.001% by mass or more and 0.2% by mass or less.

[organic medium]

The conductive composition formulated in the above manner may be provided by a silver powder, a cerium-containing composition, and a solid powder form of a valence valence adjusting material (typically in a state of a mixture), but may be dispersed, for example, in an organic medium. Provided by status. That is, the conductive composition may contain an organic medium as a component other than the solid component. The organic medium can be used as long as the solid component, particularly the silver powder, can be well dispersed, and the conventional organic medium for such a paste can be used without particular limitation. Typically, an organic vehicle in which an organic binder is dispersed in a solvent can be considered. For example, as the solvent constituting the organic medium, one type or a combination of a plurality of ethylene glycol and a diethylene glycol derivative (glycol ether type solvent), toluene, xylene, and butyl carbitol (BC) may be used. A high boiling organic solvent such as terpineol. Further, as the organic binder, various resin components may be contained. The resin component is not particularly limited as long as it can impart good adhesion to the conductive composition and coating film forming ability (adhesion to the substrate), and a conventional resin component for such a paste can be used without particular limitation. For example, an acrylic resin, an epoxy resin, a phenol resin, an alkyd resin, a cellulose polymer, a polyvinyl alcohol, a rosin resin, etc. are mentioned. Among them, a cellulose-based polymer such as ethyl cellulose is particularly preferred.

The ratio of the organic medium to the entire conductive composition (solid content + organic medium) is preferably 5% by mass or more and 60% by mass or less, preferably 7% by mass or more and 50% by mass or less, and more preferably 10% by mass or more. And 40% by mass or less. In addition, the organic binder contained in the vehicle may be contained in an amount of about 1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, based on the total amount of the conductive composition. By adopting this configuration, it is easy to use as an electrode (film) on the substrate. On the other hand, it is preferable to form (coat) a coating film having a uniform thickness, which is easy to handle, and drying before calcining the electrode film is preferably carried out without drying for a long period of time.

Furthermore, a form in which a solid component is dispersed in an organic medium (may be called The conductive composition of the paste, ink, or the like can be preferably adjusted by, for example, the following method.

That is, the prepared silver powder, the cerium-containing composition, and the valence number adjusting material are dispersed in an organic medium. Typically, the dispersion of the solid component in an organic medium can be carried out, for example, using a three-roll mill or another kneader, and the silver powder, the ruthenium-containing composition, and the valence number adjusting material of the specific blending ratio are mixed with the vehicle liquid. Mix and stir. Furthermore, when mixing the above materials, all the materials may be mixed at the same time, or may be added in two or more times. For example, the silver powder and the ruthenium-containing composition (excluding the ruthenium-supporting glass) may be mixed in advance, and then the ruthenium-supporting glass or the ruthenium number adjustment material may be added. Further, a part of the material may be mixed and dispersed in a form of a dispersion liquid such as an aqueous solvent or an alcohol. Thereby, a conductive composition in a form in which a solid component is dispersed in an organic medium can be preferably prepared.

[碲 Preparation for supporting glass]

Further, in the ruthenium-containing composition, the ruthenium-supporting glass can be prepared, for example, by mixing a specific glass powder with a ruthenium compound and calcining the mixture. The calcination is preferably carried out at a temperature range of (Tm-35) ° C to (Tm + 20) ° C in an oxidizing gas atmosphere (for example, an atmospheric environment) when the melting point of the glass powder is Tm ° C. . If the calcination temperature exceeds (Tm + 20) ° C, the glass powder is melted, and the ruthenium compound is incorporated (dissolved) in the glass phase, which is not preferable. Calcination temperature More preferably, it is (Tm+15) ° C or less, and further preferably Tm ° C or less (that is, the melting point of the glass powder or less). Further, when the calcination temperature is lower than (Tm - 35) ° C, the possibility that the antimony compound cannot be reliably supported is increased, which is not preferable. The calcination temperature is preferably (Tm - 30) ° C or more, more preferably (Tm - 20) ° C or more. Thereby, the crucible-supporting glass disclosed herein can be prepared.

Furthermore, the crucible-supporting glass which is a calcined product obtained after calcination can also be stored. A case where a large aggregate is formed by sintering as a whole. In such a case, the aggregate may be pulverized and sieved as necessary, and a particle size (for example, about 0.01 μm to 10 μm) suitable for preparation of the conductive composition may be used. By sintering, the glass powder is combined with the bismuth compound to form a neck. Although the bonding is stronger than the adhesion formed by adsorption or the like, the glass powder is not pressed against the bismuth compound, but is directly sintered in a mixed state. Therefore, the aggregate can be borrowed without using a special device such as a ball mill or a pulverizer. The granulation is easily granulated to a desired particle size by a light pulverization (for example, by manual crushing or by light mixing using a mortar and pestle).

[Production of electrodes]

The conductive composition obtained in the above manner can be operated in the same manner as the silver paste or the like which is used to form an Ag electrode as a light-receiving surface electrode on the substrate, for example. That is, the formation of the electrode by the conductive composition disclosed herein can be carried out by a conventionally known method without particular limitation.

As a method of forming the light-receiving surface electrode 12, for example, a so-called burn-through method in which the anti-reflection film 14 is formed on substantially the entire surface of the surface of the ruthenium substrate 11 and the light-receiving surface electrode 12 above the anti-reflection film 14 can be used. Forming a part directly coated with silver paste Calcination is performed to melt the anti-reflection film 14 under the silver paste to form electrical contact between the silver paste and the ruthenium substrate 11.

For example, when a silver electrode (light-receiving surface electrode 12) in the solar cell 10 shown in FIG. 1 is formed by a burn-through method, an n ⁺ layer 16 or an anti-reflection is formed on the light-receiving surface of the substrate in the same manner as in the prior art. After the reflection film 14, the conductive composition of the present invention is supplied (coated) on the anti-reflection film 14 so as to have a desired film thickness (for example, about 20 μm) or a desired coating film pattern. Typically, the supply of the conductive composition can be carried out by a screen printing method, a dispenser coating method, a dip coating method, or the like. Further, as the substrate, a substrate 11 made of bismuth (Si) is preferable, and is typically a Si wafer. The thickness of the substrate 11 can take into consideration the size of the solar cell required, or the thickness of the Ag electrode 12, the back surface electrode 20, the anti-reflection film 14 and the like formed on the substrate 11, and the strength (for example, the breaking strength) of the substrate 11. Set it up. The thickness of the substrate 11 is, for example, usually 100 μm or more and 300 μm or less, preferably 150 μm or more and 250 μm or less, and for example, 160 μm or more and 200 μm. Further, the present conductive composition can also be applied to the substrate 11 having a shallow emitter structure having a thin n ⁺ layer 16 and a low dopant concentration.

The conductive composition disclosed herein may be, for example, mainly silver powder, and The glass component containing the ruthenium-containing composition is dispersed in an organic medium. Such a conductive composition causes the ohmic contact of the silver component in the composition with the n-Si layer 16 by destroying the anti-reflection film 14 during the calcination by the glass component in the composition. By this method, the number of steps can be reduced as compared with the electrode forming method accompanying partial removal of the anti-reflection film 14, and there is no need to worry about the removed portion of the anti-reflection film 14 and the light-receiving surface electrode 12. The formation position is deviated. Therefore, the formation of the light-receiving electrode 12 can preferably employ the burn-through method.

Further, in the case where the burn-through method is not employed, for example, the following method can be employed. That is, first, the n ⁺ layer 16 or the anti-reflection film 14 is formed by chemical vapor deposition (CVD) equal to the light receiving surface on substantially the entire surface of the surface of the ruthenium substrate 11. Thereafter, the formation portion of the light-receiving surface electrode 12 in the anti-reflection film 14 is peeled off (removed) using hydrofluoric acid (hydrogen fluorite (HF)) or the like in accordance with a desired electrode pattern. Then, a conductive composition is supplied to the peeled portion at a desired film thickness.

Then, the coating material (coating film) of the conductive composition supplied to the substrate 11 is dried at an appropriate temperature (for example, at room temperature or higher, typically about 100 ° C). After drying, it is heated in a suitable calcination furnace (for example, a high-speed calciner) under suitable heating conditions (for example, 600 ° C or more and 900 ° C or less, preferably 700 ° C or more and 800 ° C or less) for a specific time. Calcination of the dried coating film. Thereby, the coating material is baked on the substrate 11 to form the silver electrode 12 as shown in FIG.

[Production of solar cells]

Further, a material or a process for manufacturing a solar cell other than the conductive composition forming electrode (typically, a light-receiving surface electrode) manufactured by the manufacturing method of the present invention may be the same as the prior art. Further, a solar cell (typically a crystalline lanthanide solar cell) having an electrode formed of the conductive composition can be produced without special treatment or the like. A typical example of the configuration of the crystalline lanthanide solar cell is the configuration shown in Fig. 1 described above.

As a process other than the formation of the light-receiving surface electrode, the formation of the aluminum electrode 20 as the back surface electrode 20 is mentioned. The order in which the aluminum electrodes 20 are formed is as follows. For example, first, as described above, the conductive composition for forming the light-receiving surface electrode 12 is printed on the light-receiving surface, and the conductive composition for forming the back-side external connection electrode 22 is printed on the back surface in the desired region. The conductive composition adjusted by the manufacturing method disclosed herein is dried and dried. Then, the aluminum electrode paste material is printed so as to be superimposed on a part of the printing region of the conductive composition for the back side external connection electrode, and dried, and the entire coating film is fired. A P ⁺ layer (BSF layer) 24 is also formed at the same time as the aluminum electrode 20 is calcined. In other words, the aluminum electrode 20 serving as the back surface electrode 20 is formed on the p-type germanium substrate 11 by firing, and the p ⁺ layer 24 containing aluminum as an impurity is formed by diffusing aluminum atoms in the substrate 11. Thereby, a solar cell (battery unit) 10 can be produced.

The conductive composition disclosed herein is controlled such that the average valence of ruthenium contained in the interface between the substrate and the electrode after firing is 4.3 or more and 5.1 or less. Since the germanium in the electronic state exists at the interface between the substrate and the electrode, the contact between the substrate and the electrode becomes good, and the electric power generated in the substrate 11 of the solar cell 10 can be extracted to the outside through the electrode with a low loss state. . Thereby, a solar cell having high energy conversion efficiency can be produced. Further, since the conductive composition contains an antimony component in nature, the strength is high, and a solar cell having high durability and reliability can be produced. Therefore, the solar cell having excellent solar cell characteristics (for example, FF of 0.78 or more and power generation efficiency of 16.5% or more) can be provided by the conductive composition.

Furthermore, the energy conversion effect of the solar cell 10 formed by the burn-through method The rate and the like are largely dependent on the quality of the ohmic contact formed in the manner described. That is, by reducing the contact resistance between the formed light-receiving surface electrode 12 and the ruthenium substrate 11, high energy conversion efficiency can be achieved. The conductive composition disclosed herein can improve ohmic contact as described above, and thus can preferably contribute to the solar cell 10 in which the fill factor (FF) or energy conversion efficiency is improved.

Moreover, in the conventional configuration of the conventional solar cell, the wavelength is short. Since light transmittance is low, there is no case where pn bonding is achieved and power generation is facilitated, but it is absorbed by the n-Si layer to become heat (heat loss). In a preferred embodiment of the solar cell 10 disclosed herein, the n-Si layer 16 can also be reduced for the purpose of delivering light of a shorter wavelength to the pn junction portion with high intensity to improve photoelectric conversion efficiency. The thickness (depth) reduces heat loss. The thickness of the n-Si layer 16 can be, for example, about 300 nm to 500 nm as in the related art. However, for example, it may be made thinner than 300 nm or less, more preferably 250 nm or less.

Generally, if the thickness of the n-Si layer becomes so thin, since the n-Si layer is The electric resistance is increased and the sheet resistance is increased, and the dopant concentration or the like is required to suppress the recombination of the surface, so that it is difficult to obtain a good ohmic contact between the light-receiving surface electrode and the n-Si layer, and the contact resistance is increased. After that. Further, when the above-described burn-through method is applied to the formation of the light-receiving electrode, the possibility that the electrode paste not only reaches the n-Si layer but also exceeds the n-Si layer and erodes to the vicinity of the pn junction interface is required, and the calcination conditions are required to be strict. And, in turn, there is a negative impact on the solar cell's fill factor (FF) or energy conversion efficiency. However, by using the conductive composition disclosed herein, formation The smooth electrode can positively improve the ohmic contact as described. Therefore, even when the thickness of the n-Si layer 16 is made thinner than 250 nm or less, or the baking condition is adjusted so as not to etch the pn junction, it is possible to suppress an increase in contact resistance and achieve good bonding.

The embodiments related to the present invention are described below, but the present invention is not intended to be limited to the following examples.

A conductive composition 1 to a conductive composition 10 containing a silver powder (average particle diameter: 1.6 μm), Ni powder (average particle diameter: 0.15 μm), and a glass composition shown below were prepared. The conductive composition is dispersed in an organic vehicle containing a binder (ethylcellulose) and an organic solvent (terpineol) and added to the organic solvent, thereby adjusting the viscosity to 160 Pa. s~180Pa. Paste in s (20 rpm, 25 ° C). The paste was prepared using a three roll mill. The formulation of the paste-like conductive composition thus obtained is as follows: silver powder: 77% by mass to 88% by mass; Ni powder: 0.01% by mass to 0.2% by mass; glass composition: 1% by mass to 10% by mass; organic medium Organic vehicle: 4% by mass to 14% by mass; organic solvent: 2% by mass to 8% by mass.

In addition, as the glass composition, the amount of the conductive composition is such that the amount of the conductive composition is a value shown by the "Te addition amount" in Table 1 below, and the basic glass medium containing no antimony and the antimony containing The glass medium is mixed and used. As the basic glass medium, a glass having an average particle diameter of 1.1 μm and having the following composition A or composition B was used. Further, as the cerium-containing glass medium, glass having the following composition was used.

<Basic glass medium: composition A>

Bi ₂ O ₃ : 20 mol%, B ₂ O ₃ : 29 mol%, SiO ₂ : 4 mol%, ZnO: 30 mol%, Li ₂ O: 17 mol%

<Basic Glass Media: Composition B>

PbO: 29 mol%, B ₂ O ₃ : 12 mol%, SiO ₂ : 47 mol%, Li ₂ O: 12 mol%

<碲-containing glass medium>

Te ₂ O: 30 mol%, PbO: 29 mol%, B ₂ O ₃ : 5 mol%, SiO ₂ : 36 mol%

[Production of Solar Cell for Evaluation]

The paste-like conductive composition 1 to the conductive composition 10 obtained above were used as a paste for forming a light-receiving surface electrode, and solar cells for evaluation were produced in the following order.

Specifically, first, a commercially available 156 mm square solar cell p-type single crystal germanium substrate (plate thickness: 180 μm) was prepared, and the surface thereof was subjected to an acid etching treatment using a mixed acid obtained by mixing hydrofluoric acid and nitric acid. Then, a phosphorus-containing solution is applied to the light-receiving surface of the ruthenium substrate having the fine uneven structure formed by the etching treatment, and heat treatment is performed to form n-thickness having a thickness of about 0.5 μm on the light-receiving surface of the ruthenium substrate. Si layer (n ⁺ layer) (refer to Fig. 1). An antireflection film (tantalum nitride film) having a thickness of about 80 nm was formed on the n-Si layer by a plasma CVD (Plasma-Enhanced Chemical Vapor Deposition (PECVD)) method.

Then, using the prepared conductive composition, a coating film (having a thickness of 10 μm or more and 30 μm or less) which is a light-receiving surface electrode (Ag electrode) is formed on the anti-reflection film by a screen printing method. Further, in the same manner, a coating film to be a back surface electrode (Ag electrode) was formed in a pattern. The coating films were dried at 85 ° C for the next step.

Then, by screen printing (SUS mesh, #325, wire diameter 23μm, The emulsion is 20 μm thick, and the same applies hereinafter, and a specific aluminum paste for a back surface electrode is printed (coated) so as to overlap a part of the Ag electrode pattern on the back side of the ruthenium substrate. The printing conditions were set so that the baking width of the gate line became 100 μm. Then, the tantalum substrate is fired in a near-infrared high-speed calciner at a temperature of approximately 700 ° C or more and 800 ° C or less in an atmospheric environment. Thereby, an evaluation solar cell including an Ag electrode (light-receiving surface electrode) was obtained. Hereinafter, the solar cells produced using the conductive composition 1 to the conductive composition 10 are referred to as samples 1 to 10, respectively.

[Filling factor (FF) and energy conversion efficiency (Eff)]

The solar characteristics of the solar cells of samples 1 to 10 were measured using a solar simulator (manufactured by Berger Co., Ltd., PSS10), and the open circuit voltage (Voc) and the filling factor (fill) were determined based on the obtained IV curve. Factor, FF) and power generation efficiency (η). The Voc, FF, and power generation efficiency were calculated based on the "method of measuring the output power of the crystalline solar cell unit" defined in JIS C-8913, and the results are shown in Table 1. Furthermore, the calculated value is the average of 100 data obtained by the solar simulator.

[Evaluation of the price of 碲]

For the solar cells of Samples 1 to 10 after the I-V characteristics were measured, the electrodes on the surface of the ruthenium substrate were peeled off, and the interface between the exposed electrodes and the substrate (the surface of the substrate) was subjected to XAFS analysis, and the valence of ruthenium in the interface was examined. The analysis conditions are as follows.

Analytical device: SPRING-8 industrial utilization II, BL14B2

Monochromator: SPring-8 standard two crystal splitter

Spectroscopic crystal: Si(111)

Measuring energy area: 4320eV~4400eV

Determination method: transmission method

In the XANES spectrum, the larger the valence of ruthenium, the more the absorption end shifts toward the high energy side. In the analysis of the valence of yttrium, TeO ₂ and TeO _{3 were} used as standard samples of tetravalent and hexavalent ruthenium, respectively, and the measurement sample was calculated based on the displacement amount of the absorption energy around 4350 eV in the XANES spectrum of the standard sample. The average price of the cesium contained. The measurement results of the average valence of hydrazine are shown in Table 1.

[Evaluation]

The valence of ruthenium in the electrode-substrate interface obtained by calcining the conductive composition of Samples 1 to 10 largely coincides with the value expected from experience. As shown in Table 1, the ratio of ruthenium contained in the conductive composition to the electrode-substrate interface after calcination It is observed that the valence of ruthenium tends to decrease as the amount of addition of Te increases. However, according to Sample 1, Sample 2, and Sample 5, such a relationship is not necessarily established, and the valence of hydrazine may vary depending on the formulation of the glass composition or the formulation of the valence number.

In addition, when the valence of 碲 is 4.3 or more and 5.1 or less, it is shown that Voc, FF, and power generation efficiency are all in good balance, and it shows the favorable value. The fill factor (FF) is basically an index that serves as a benchmark for solar cell quality, and a representative FF value is in a range of 0.7 or more and 0.8 or less. In the latter half of the FF value higher than 0.7, even if the FF value is increased by 0.01%, the performance as a solar cell can be greatly improved. From the results of Table 1, it was confirmed that the obtained FF value has a large difference depending on the valence of ruthenium in the conductive composition. In other words, when the valence of 碲 is 4.3 or more and 5.1 or less, the FF value is higher than 0.78, and an extremely high value can be obtained as compared with other cases.

Further, the same tendency tends to be observed for Voc and power generation efficiency. When the valence of ruthenium is 4.3 or more and 5.1 or less, it is considered that the characteristics are well balanced and remarkably improved.

The specific examples of the present invention have been described in detail above, but these are merely illustrative and are not intended to limit the scope of the application. The technology described in the patent application scope includes various modifications and changes to the specific examples described above.

10‧‧‧Solar battery

11‧‧‧Substrate

12‧‧‧Photometric surface electrode (Ag electrode)

14‧‧‧Anti-reflective film

16‧‧‧n-Si layer (n ⁺ layer)

20‧‧‧Back electrode (aluminum electrode)

22‧‧‧Electrode for external connection on the back side

24‧‧‧p ⁺ layer (BSF layer)

Claims (7)

A method for producing a conductive composition, wherein the conductive composition is an electrode for forming a solar cell, and the method for producing the conductive composition comprises: preparing a silver powder, a ruthenium-containing composition, and a ruthenium number adjusting material The average valence of cerium (Te) contained in the interface between the substrate and the conductive composition when the conductive composition is applied to the substrate of the solar cell and fired is 4.3 or more Further, in a mode of 5.1 or less, the composition of the silver powder, the ruthenium-containing composition, and the valence number adjusting material is adjusted to prepare a conductive composition. The method for producing a conductive composition according to the first aspect of the invention, wherein the cerium-containing composition is a cerium compound powder containing cerium (Te) as a constituent element. The method for producing a conductive composition according to the first or second aspect of the invention, wherein the cerium-containing composition is a glass composition containing cerium (Te) as a constituent element. The method for producing a conductive composition according to claim 3, wherein the glass composition is a mixture of a basic glass component containing no antimony and a hafnium containing glass component containing antimony. The method for producing a conductive composition according to any one of claims 1 to 4, wherein the valence number adjusting material comprises a material selected from the group consisting of titanium (Ti), vanadium (V), and manganese ( a metal or a metal compound of at least one metal element in the group consisting of Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn). A conductive composition produced by the method for producing a conductive composition according to any one of the first to fifth aspects of the invention. A solar cell comprising an electrode formed using the conductive composition according to claim 6 of the patent application.